A glass melting furnace typically comprises a steel shell with a lining of refractory bricks. A high volume glass furnace, such as a furnace designed to make bottles, television panels or windows, can be quite large and require 1 or 2 thousand tons of refractory bricks for its lining. These refractory bricks are chemically and physically stable while in contact with molten glass at high temperatures. That is, to provide extended furnace life and to preserve the targeted glass composition, the refractories should not react with or dissolve in the molten glass nor should they melt, crack, spall or deform at molten glass temperature.
The most common refractory bricks have, as their main constituent, an oxide of silicon, aluminum, zirconium or chromium. Furnace linings of silica brick, alumina firebrick or zirconia brick are suitable for most glass compositions. Zirconia refractories may be used in furnaces making glasses having a higher softening temperature.
A furnace carefully constructed of properly manufactured refractories has a typical life of 3 to 6 years. Corrosion, erosion and mechanical failure due to thermal shock eventually wear out the refractory lining. At the end of the useful life of the lining, the furnace is shut down, the used lining removed and a new lining installed.
Disposing of the used lining presents several problems. The mass of material is large, averaging 1000 to 2000 tons per year for a factory operating 2 or 3 high volume glass furnaces. The amount of available landfill space makes such disposal a concern. Also, the increasingly expensive cost of landfill disposal makes this an expensive component of operating a glass furnace.
Furthermore, having been a container for molten glass, the used refractory material typically contains particles of the glass and chemicals from the glass. Lead glasses and glasses which use arsenic as a refining agent constitute hazardous waste and must therefore be treated and disposed of in a special manner. This adds the concerns of environmental impact and liability, as well as an even more expensive disposal cost, to glass furnace operation.
Therefore, a need exists for a method of safely and inexpensively disposing of or utilizing used refractory linings from glass melting furnaces.